Hyperspectral Model of Solar Radiation Transport in an Atmosphere with Cirrus Clouds

The radiation transfer theory, based on different approximations of the Boltzmann kinetic equations, is the theoretical basis for Earth remote sensing from space and radiation forcing on the climate. A fast line-by-line model (FLBLM) of solar radiation transport in a cloudy atmosphere (improved with account for the high resolution of absorption spectra in the IR range, aerosol scattering and absorption, polarization effects, and heterogeneous and anisotropic media) is proposed. The FLBLM model, focused on the local calculations and express analysis, is implemented by statistical modeling using the algorithms of the Monte Carlo method. A hyperspectral calculation of the Stokes vector function of outgoing solar radiation in an atmosphere with cirrus clouds above cumulonimbus clouds has been performed, which makes it possible to evaluate the influence of cirrus clouds and their microphysics on spectral polarization. Models with six independent parameters in the phase matrix are used for cirrus clouds for various effective particle diameters from 10 to 120 μm, while cumulonimbus droplet clouds are described by a model with four independent parameters and an effective droplet diameter of 62 μm.